Electric shavers usually have one or more cutter elements driven by an electric drive unit in an oscillating manner where the cutter elements reciprocate under a shear foil, wherein such cutter elements or undercutters may have an elongated shape and may reciprocate along their longitudinal axis. Other types of electric shavers use rotatory cutter elements which may be driven in an oscillating or a continuous manner. Said electric drive unit may include an electric motor or a magnetic-type linear motor, wherein the drive unit may include a drive train having elements such as an elongated drive transmitter for transmitting the driving motion of the motor to the cutter element, wherein said motor may be received within the handle portion of the shaver or in the alternative, in the shaver head thereof.
Irrespective of the architecture of the drive unit and the drive train, the cutter elements, in addition to the aforementioned cutting motion, may be movable in other directions so as to self-adapt to the contour of the skin to be shaved. For example, the cutter elements may be part of a shaver head that is slewable about one or more axes relative to the handle of the shaver, wherein the support structure connecting the shaver head to the handle may allow the shaver head to swivel about a swivel axis extending substantially parallel to the elongated cutter elements and/or the reciprocating axis thereof. In addition or in the alternative, the supporting structure may allow the shaver head to tilt about a tilting axis extending transverse to the longitudinal axis of the handle and transverse to the elongated cutter elements and/or the reciprocating axis thereof. In addition to or in the alternative to such shaver head movements, the cutter elements may dive into the shaver head so as to adjust the position relative to the skin contour to be shaved.
Due to the slewing movements of the shaver head and its cutter elements relative to the handle, transmission of the driving movements from a motor to the cutter elements is sometimes difficult, in particular when the drive unit includes a motor accommodated in the handle and connected to the cutter elements in the shaver head via a drive train that needs to compensate for the tilting and/or swiveling movements of the cutter elements relative to the handle and thus, relative to the motor in the handle. Such compensation may be achieved by flexible elements in the drive train allowing for misalignment of the cutter element's coupling to the drive train and a drive train portion fixedly aligned with the handle. Another compensation approach is to provide for play in a coupling part, for example a drive pin received in a slot-like recess such as an oblong hole. However, such compensation of the tilting or swiveling movements through flexible elements or play reduces efficiency of power transmission and limits the achievable oscillation frequencies.
For example, US 2009/0025229 A1 discloses an electric shaver having a pair of cutter elements provided under a shear foil and driven in an oscillating manner along a cutter oscillation axis, wherein the oscillating driving movements of transmitter pins extending into the shaver head are applied onto the cutter elements via an oscillatory bridge supported for oscillatory reciprocation in said shaver head, wherein said oscillatory bridge includes yielding coupling arms so as to compensate for the adjusting movements of the cutter elements. Due to the rather complex shape of the oscillatory bridge, however, the transmission architecture is rather complicated, bulky and difficult to clean. Moreover, the yielding structure of the oscillatory bridge is power-consuming and detrimental to achieving high frequencies of oscillation of the cutter elements.
A similar transmission architecture including an oscillation bridge of a pivoting type is known from U.S. Pat. No. 7,841,090 B2.
Due to the limited space available in the shaver head and the rather bulky structure of such oscillation bridges, it is also difficult to avoid a collision of the drive train with the support structure allowing slewing of the shaver head. Of course, such drive train could be significantly reduced in size and the compensation of misalignments could easily be avoided by means of accommodating the entire drive unit including the motor in the shaver head. However, such approach significantly increases the weight of the shaver head and thus, its responsiveness to contour changes, and in addition, handling of the shaver is impaired due to unbalanced mass. So as to avoid such collision between the drive train extending from the handle into the shaver head, it has been tried to reduce the support structure for the shaver head in size. Such support structure connecting the shaver head to the handle may have different configurations so as to allow for the aforementioned swiveling and/or tilting movements and to avoid collisions with the drive train extending from the drive unit to the cutter element. For example, prior art reference US 2010/0175264 A1 shows a four-joint linkage of the shaver head to the handle, wherein link arms are arranged in a sort of pendulum or hanging arrangement. An interposer part attached to the handle includes two poles projecting upwards into the shaver head, wherein the link arms are pivotably attached to the top end portions of such poles to extend or hang downwards back towards to the handle. The lower end portions of such hanging link arms are pivotably connected to a shaver head frame.
A similar support structure movably connecting the shaver head of an electric shaver to the handle thereof is shown by reference JP 2016-77464 A also showing a four-joint linkage including a pair of hanging link arms.
Another shaver allowing for swiveling and tilting of the shaver head of an electric shaver about swiveling and tilting axes is shown by EP 2 435 218 B1 suggesting a cardanic support structure including a shaver head frame pivotably mounted to a cradle-like handle part and, on the other hand, pivotably supporting a cutter frame on which the cutter element is supported.
Furthermore, AT 409604 B shows an electric shaver having cutter elements which may, in addition to the oscillating cutting movements, pivot about an axis perpendicular to the shaver's longitudinal axis and the axis of oscillation of the cutter element so as to allow for adjustment of the cutter element position to the skin to be shaved, and rotatorily oscillate about an axis parallel to the longitudinal axis of the shaver housing. The transmission train connecting the drive motor to the cutter elements includes a coupling structure rotatorily oscillating about a pivot axis parallel to the shaver housing's longitudinal axis.
US 2009/0025229 A1 discloses a drive unit for the cutter elements of an electric shaver, wherein the drive unit includes transmitter pins extending from the shaver housing towards the shaver head, wherein the oscillating driving movements of said transmitter pins are applied onto the cutter elements via an oscillatory bridge supported for oscillatory reciprocation in the shaver head, wherein said oscillatory bridge includes yielding coupling arms so as to allow for adjusting movements of the cutter elements. A similar transmission architecture is known from U.S. Pat. No. 7,841,090 B2.
Further electric shavers allowing for adapting movements of the cutter elements are known from U.S. Pat. No. 3,748,371 B, FR 1391957 A, GB 811,207 B and U.S. Pat. No. 5,704,126 B.